Modulation in high frequencies and antennas

Hi to everyone. I have heard that we usually prefer to modulate signals at high frequencies so the wave length is small compared to the length of the antenna. Is there any rule or equation that implies this requirement?

Staff: Mentor

To be an efficient radiator, an antenna will generally be a half-wave dipole or a quarter-wave monopole. That is, a dipole antenna will have two opposed elements, each a quarter-wavelength long. A monopole will have a single radiating element a quarter-wavelength long, over some ground plane or set of ground elements.

Hi to everyone. I have heard that we usually prefer to modulate signals at high frequencies so the wave length is small compared to the length of the antenna. Is there any rule or equation that implies this requirement?

Modulation has little to nothing to do with the antenna. The carrier frequency and the antenna are related as berkeman pointed out.

So you are saying that the reason we use certain frequencies in the spectrum for the carrier is to keep the antenna size in check? The main reason we use the ones we do is propagation of the wave. Some signals we want to go over the horizon, some we don't. Some signals we want refracted off the ionosphere, some we don't. However, there ARE cases were antenna size is a consideration. I would not say it is the main reason. Throwing the word modulation in there has thrown me off.